Download 3G Wireless Systems

3G Wireless Systems
Nachiket Mehta
Wireless Networks CSG250
OUTLINE

3G Overview
• Advantage, Capabilities, Organizations, IMT2000 radio interface, Technologies, Evolution
paths

UMTS-FDD / WCDMA
• Spreading Codes, Physical layer, Mac layer, RLC
layer, RRC layer
• Hand Over
• Power Control
• QoS Support



What’s next after 3G?
Summary
References
3G Overview
Route to 3G


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
1G: analog
2G : 1st digital mobile telephony
2.5G: transition from 2G to 3G
3G standard: IMT 2000
3G & Future Wireless Vs. Bandwidth
10,000,000,000
4G
1,000,000,000
100,000,000
3.5G
bps
10,000,000
3G
1,000,000
GPRS
100,000
2G
10,000
1,000
100
1960
1970
1980
1990
2000
2010
3G- Advantages
3G phones promise : Improved digital voice communications
 Larger Bandwidth – Higher Data rate
 Greater subscriber capacity
 Fast packet-based data services like e-mail, short message
service (SMS), and Internet access at broadband speeds.
 Most carriers also expect consumers to want :•
•
•
•
•
location services
interactive gaming
streaming video
home monitoring and control
and who knows what else, while being fully mobile anywhere in the
world.
3G Capabilities





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Voice quality comparable to the public switched
telephone network
144 Kbps- user in high-speed motor vehicles
384 Kbps- pedestrians standing or moving slowly
over small areas
Up to 2 Mbps- fixed applications like office use
Symmetrical/asymmetrical data transmission rates
Support for both packet switched and circuit switched
data services like Internet Protocol (IP) traffic and
real time video
Organizations
• 3G is also known as UMTS (Universal Mobile
Telecommunication System)
• 3GPP 3rd Generation Partnership Project.
• 3GPP2 3rd Generation Partnership Project 2
• Internet Engineering Taskforce (IETF)
• ITU-IMT-2000 Standard (International
Telecommunication Union- International Mobile
Telecommunication)
IMT-2000 Radio Interface
IMT
Unpaired Spectrum
Paired Spectrum
IMT-DS
UMTS-FDD
(WCDMA)
Direct spread
IMT-MC
CDMA-2000
(1x-EvDO/DV)
Multi carrier
CDMA
IMT-TC
UMTS-TDD
(TD-SCDMA)
Time code
TDMA
IMT-SC
UWC-136
(EDGE)
Single carrier
IMT-FT
DECT
Freq. time
FDMA
IMT-2000 Frequency Bands
1G + 2G
806
960 MHz
2G (Asia, Europe) + 3G
1885 MHz
1710
WCDMA(UL) 1820-1880MHz
WCDMA(DL) 1910-1970MHz
DECT, PHS + 2G + 3G
1885
2500
2025
2110
2200 MHz
2690 MHz
Technologies

3G is superior to the other digital standards like:• GSM (Global System for Mobile) communications standard used worldwide
• And IS-136 TDMA standard used primarily in North America.

3G Technologies:• WCDMA or UMTS-FDD (Universal Mobile Telecommunications System Frequency Division Duplex)---Direct Spread
• CDMA2000 - 1x-EvDO/EvDV---Multi carrier
• UMTS – TDD (Time Division Duplex) or TD-SCDMA (Time Division Synchronous Code Division Multiple Access) ---Time Code

4G Technologies:• Digital Audio Broadcast (DAB) and Digital Video Broadcast (DVB) for wide
area broadcasting
• Local Multipoint Distribution System (LMDS)
• Microwave Multipoint Distribution System (MMDS)
Wireless Technologies (Figure)
Evolution Paths
cdmaOne
IS-95A
cdmaOne
IS-95B
Cdma2000 1X
Cdma2000
1xEV-DO
Cdma2000
1xEV-DV
TDMA
IS-41 Core Network
EDGE
GSM
GPRS
GSM Map Core Network
2G
2.5G
3G
WCDMA
UMTS-FDD / WCDMA
(Universal Mobile
Telecommunication StandardFrequency Division Duplex)
UMTS-FDD / WCDMA
Wideband Direct Sequence Code Division
Multiple Access
 Does not assign a specific frequency to each
user. Instead every channel uses the full
available spectrum. Individual conversations
are encoded with a pseudo-random digital
sequence
 Narrowband option for TDD.

WCDMA Parameters
Channel B.W
5 MHz
Forward RF Channel Structure
Direct Spread
Chip Rate
3.84 Mcps
Frame Length
10 ms (38400 chips)
No. of slots/frame
15
No. of chips/slot
2560chips (Max. 2560 bits)
Power Control
Uplink SF
Open and fast close loop (1.6
KHz)
4 to 256
Downlink SF
4 to 512
Spreading Operation


Spreading means increasing the signal bandwidth
Strictly speaking, spreading includes two operations:
(1) Channelisation (increases signal bandwidth)
- using orthogonal codes
(2) Scrambling (does not affect the signal bandwidth)
- using pseudo noise codes
Codes
Channellization Code
Scrambling Code
Usage
UL: Separation of physical data
and control channels from same UE
DL: Separation of different users
within one cell
UL: Separation of terminals
DL: Separation of
cells/sectors
Length
UL:4-256 chips
DL:4-512 chips
38400 chips
No. of
codes
No. of codes under one scrambling code=
SF
UL: Several million
DL: 512
Code
Family
Orthogonal Variable Spreading Factor
Long 10ms code: Gold
code
Short code: Extended S(2)
code Family
Increase
B.W?
YES
NO
UMTS/IMT-2000 Architecture
UMTS Protocol Stack
WCDMA : PHYSICAL Layer
Physical Layer

The physical layer offers information transfer services to the
MAC layer. These services are denoted as Transport channels
(TrCh’s). There are also Physical channels.

Physical layer comprises following functions:
•
•
•
•
•
•
•
􀂉 Various handover functions
􀂉 Error detection and report to higher layers
􀂉 Multiplexing of transport channels
􀂉 Mapping of transport channels to physical channels
􀂉 Fast Close loop Power control
􀂉 Frequency and Time Synchronization
􀂉 Other responsibilities associated with transmitting
and receiving signals over the wireless media.
Transport & Physical Channels
Transport Channel
Physical Channel
(UL/DL) Dedicated Channel DCH
Dedicated Physical Data Channel DPDCH
Dedicated Physical Control Channel DPCCH
(UL) Random Access Channel RACH
Physical random access channel PRACH
(UL) Common packet channel CPCH
Physical common packet channel PCPCH
(DL) Broadcast channel BCH
Primary common control physical channel P-CCPCH
(DL) Forward access channel FACH
(DL) Paging channel PCH
Secondary common control physical channel S-CCPCH
(DL) Downlink shared channel DSCH
Physical downlink shared channel PDSCH
Signaling physical channels
Synchronization channel SCH
Common pilot channel CPICH
Acquisition indication channel AICH
Paging indication channel PICH
CPCH Status indication channel CSICH
Collision detection/Channel assignment indicator
channel CD/CA-ICH
WCDMA : MAC Layer
MAC Layer


The MAC layer offers Data transfer to RLC and higher layers.
The MAC layer comprises the following functions:
• Selection of appropriate TF (basically bit rate), within a predefined set,
per information unit delivered to the physical layer
• Service multiplexing on RACH, FACH, and dedicated channels
• Priority handling between ‘data flows’ of one user as well as between
data flows from several users—the latter being achieved by means of
dynamic scheduling
• Access control on RACH
• Address control on RACH and FACH
• Contention resolution on RACH
WCDMA : RLC Layer
RLC Layer

The RLC layer offers the following services to the higher
layers:
• Layer 2 connection establishment/release
• Transparent data transfer, i.e., no protocol overhead is appended to the
information unit received from the higher layer
• Assured and un assured data transfer

The RLC layer comprises the following functions:
• Segmentation and assembly
• Transfer of user data
• Error correction by means of retransmission optimized for the
WCDMA physical layer
• Sequence integrity (used by at least the control plane)
• Duplicate detection
• Flow control
• Ciphering
WCDMA : RRC Layer
RRC Layer

The RRC layer offers the core network the following services:
• General control service, which is used as an information broadcast
service
• Notification service, which is used for paging and notification of a
selected UEs
• Dedicated control service, which is used for establishment/release of a
connection and transfer of messages using the connection.

The RRC layer comprises the following functions:
• Broadcasting information from network to all UEs
• Radio resource handling (e.g., code allocation, handover, admission
control, and measurement reporting/control)
• QoS Control
• UE measurement reporting and control of the reporting
• Power Control, Encryption and Integrity protection
WCDMA : Hand Over
Hand Over

Intra-mode handover
• Include soft handover, softer handover and hard
handover.
• Rely on the Ec/No measurement performed from
the CPICH.

Inter-mode handover
• Handover to the UTRA TDD mode.

Inter-system handover
• Handover to other system, such as GSM.
• Make measurement on the frequency during
compressed mode.
WCDMA : Power Control
Power Control

Fast Closed Loop PC – Inner Loop PC
• Feedback information.
• Uplink PC is used for near-far problem. Downlink PC is to
ensure that there is enough power for mobiles at the cell
edge.

Two special cases for fast closed loop PC:
• Soft handover:- how to react to multiple power control
commands from several sources. At the mobile, a “power
down” command has higher priority over “power up”
command.
• Compressed mode:- Large step size is used after a
compressed frame to allow the power level to converge
more quickly to the correct value after the break.
Power Control (Contd.)

Open loop PC
• No feedback information.
• Make a rough estimate of the path loss by means
of a downlink beacon signal.
• Provide a coarse initial power setting of the mobile
at the beginning of a connection.
• Apply only prior to initiating the transmission on
RACH or CPCH.
WCDMA : QoS Support
UMTS/WCDMA QoS
The standard provides an overview of the
functionality needed to establish, modify and
maintain a UMTS link with a specific QoS.
 Divided into:

• Control plane

Managing, translating, admitting and controlling users
requests and network resources.
• User plane

QoS signaling and monitoring of user data traffic
QoS Classes

Conversational (real time):• VoIP
• Telephony
• Video conferencing

􀂉 Streaming (real time):• Video and audio streams

􀂉 Interactive:• Web browsing
• Data retrieval
• Server access

􀂉 Background:• Download of emails and files
What next after 3G?
• The future path has fractured
into a number of possibilities
• Operators and vendors must
create viable strategies to
prosper within this complexity
2.5G &
WLAN
3G &
WLAN
GPRS/
EDGE
(2.5G)
GSM
(2G)
1990
3G &
WLAN &
Brdcst
3G &
WLAN &
Ad-hoc
3G+ &
WLAN
4G &
WLAN &
Brdcst
4G &
3G+ &
WLAN & WLAN &
Ad-hoc Ad-hoc
4G &
WLAN
3G+
W-CDMA
(3G)
2000
4G
2010
4G Air Interface
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Higher bit rates than 3G (20 Mbps < peak < 200 Mbps)
Higher spectral efficiency and Lower Cost per bit than 3G
Air interface and MAC optimized for IP traffic
• Adaptive modulation/coding with power control, hybrid ARQ
Smaller cells, on average, than 3G
• However, cell size will be made as large as possible via:
 High power base station to boost downlink range
 Asymmetry - used to boost uplink range when necessary
 Adaptive antennas option
Higher frequency band than 3G (below 5 GHz preferred)
RF channel bandwidths of 20 MHz and higher
Frequency Domain methods:
• OFDM is promising for downlink
OFDM
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Divides the spectrum into a number of equally spaced tones.
Each tone carries a portion of data.
A kind of FDMA, but each tone is orthogonal with every other
tone. Tones can overlap each other.
Example: 802.11a WLAN
Summary

3G wireless services are rapidly spreading the global market place with CDMA as the
preferred technology solution

The following are the key 3G Technologies that have emerged to be the key commercial
players:
•
CDMA2000 1X
•
CDMA2000 1xEV-DO
•
UMTS/WCDMA

WCDMA is one of them, which provides:• Larger Bandwidth – Higher Data rate – Lower cost
• Greater subscriber capacity
• IMT-2000 Radio interface standard offers 3G standard
• Hand Over, Power Control problems are addressed
• QoS offered But Customers really want them?

4G still in a formative stage (commercial 2010)
Frequency bands less than 5 GHz preferred for wide-area, mobile services
4G system bandwidth between 20 and 100 MHz
Lower cost per bit than 3G
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References
Websites:
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http://www.sss-mag.com
www.electronicdesign.com
www.3g-generation.com
www.3gtoday.com
http://www.pctechguide.com
Articles:
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Latest Trends and New Enhancements in 3G Wireless Communications- By Rao Yallapragada, QualComm
WCDMA—The Radio Interface for Future Mobile Multimedia Communications-By Erik Dahlman, Per
Beming, Jens Knutsson, Fredrik Ovesj¨o, Magnus Persson, and Christiaan Roobol
UMTS -Mobile Telematics 2004-Anne Nevin
Fourth Generation Cellular Systems:
Spectrum Requirements-By Joseph M. Nowack-Motorola Labs
IMT Project. What is IMT-2000, Geneva-2001
WCDMA-Physical Layer- By Peter Chong, Ph.D. (UBC, Canada)
3G-4G wireless, COMPT 880 Presentation- By Simon Xin Cheng,Simon Fraser University
THANK YOU!
Wireless Networks CSG250